H1N1 influenza damages upper and lower airways
MedWire News: Results from a US autopsy study show that the H1N1 influenza virus (swine flu) can damage cells throughout the entire respiratory tract.
"This pattern of pathology in the airway tissues is similar to that reported in autopsy findings of victims of both the 1918 and 1957 influenza pandemics," commented lead researcher Jeffery Taubenberger, from the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Maryland, USA.
Taubenberger and team reviewed autopsy reports, hospital records, and other clinical data on 34 people who died of H1N1 influenza between May and July 2009. All but two of the deaths occurred in New York.
Examination of tissue samples revealed damage to cells in the trachea and bronchial tubes in all cases. Furthermore, there was evidence of damage to the bronchioles in 18 cases, and damage to the alveoli in the lungs in 25 cases.
The researchers identified evidence of pulmonary bacterial infections in 55% of cases. However, not all of those individuals who had bacterial pneumonia along with H1N1 influenza had been hospitalized, indicating that community-acquired bacterial pneumonia may play a role in the current pandemic.
"Even in an era of widespread and early antibiotic use, bacterial pneumonia remains an important factor for severe or fatal influenza," the authors comment.
They also note that 91% of the patients who died had underlying medical conditions, such as heart disease and asthma, and 72% were obese. This latter observation is in line with earlier reports linking obesity with an increased risk for death from H1N1 influenza, notes the team.
The study also underscores the impact of H1N1 influenza on younger age groups. Indeed, whereas most deaths from seasonal influenza occur in adults over 65 years of age, 62% of the 34 patients who died from H1N1 influenza in the current study were aged 25–49 years, and two were infants.
Taubenberger and team conclude: “The pulmonary pathologic findings in fatal disease caused by the novel pandemic influenza virus are similar to findings identified in past pandemics.”
Anthony Fauci, director of the NIAID, commented: “This study provides clinicians with a clear and detailed picture of the disease caused by 2009 H1N1 influenza virus that will help inform patient management.
"In fatal cases of 2009 H1N1 influenza, it appears the novel pandemic influenza virus produces pulmonary damage that looks very much like that seen in earlier influenza pandemics."
The research is published in the Archives of Pathology and Laboratory Medicine.
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2009
By Mark Cowen